The disclosure generally relates to power over fiber technology having the ability to provide electrical power and communications via fiber to one or more sensors of one or more varieties. More particularly, the disclosure relates to a sensor system capable of producing electrical power by using a photovoltaic power converter and at least one sensor.
Power over fiber (PoF) technology supplies power via light (e.g. laser light, LED light, etc.) sent through fiber optic cables to a photovoltaic power converter (PPC) that converts the laser light into a continuous supply of electrical power for sensors and other electrical devices. Light is sent through a non-conductive fiber optic cable (to provide power) to a destination where the transmitted laser light is then converted to electricity by the PPC. The non-conductive fiber optic cable provides benefits such as high voltage isolation, electrical noise immunity, lightning strike risk reduction, and light weight.
Sensors are often required in remote places, away from an easily available source of power, or are required in locations that are hazardous or hard to reach, or in high voltage or electrically noisy environments. Conventional techniques of providing power to these sensors include batteries, copper wire (when voltage isolation or noise immunity is not required), isolation transformers, as well as energy harvesting techniques. These techniques each suffer from limitations including operating duration (e.g. battery life), noise sensitivity (e.g. copper wire and isolation transformers), and low power levels (e.g. low battery power or energy harvesting).
Partial discharge (PD) is a phenomena that occurs when air on a conductor or insulator is ionized, thus resulting in corona (i.e., current flow through the ionized air), or when discharges occur between conductors. PD can degrade the insulation and other components within switchgear cabinets, electrical cabinets, motors, transformers, generators or other high or medium voltage compartments or electrical devices, insulators, substations, and other areas, and can lead to catastrophic arc flash events. Such failures in switchgear or similar devices can cause power outages, equipment damage, and injury.
More particularly, switchgear cabinets generally have multiple high voltage (HV) compartments, each compartment housing different equipment serving a different function. Generally, PD events are most likely to occur at locations where insulation material degrades, but they can also occur at points of mechanical connections and other such locations that are subject to mechanical wear. Within a switchgear cabinet, these mechanical connections may be where bus bars make connections and/or where physical contacts are made (such as for breakers or switches). Temperature and humidity are both factors that lead to electrical accidents within switchgear cabinets. High temperatures are indicative of electrical current overloads or high impedance, which can be a sign or the cause of insulation breakdown, while high humidity contributes to the rapid deterioration of insulation.
For switchgear cabinets, PD is traditionally measured by antennas that are placed within high voltage compartments, typically on a wall. These antennas “listen” for acoustic events (e.g. sound that is generated from sparking), or detect UHF signals generated by a PD event. When a PD event is detected, a corresponding signal from the detecting sensor is transmitted back to a data controller and processed for monitoring. While the earlier-described partial discharge (PD) detection systems are able to detect when PD events occur, they cannot detect where an event occurs, for example within a high voltage (HV) compartment. Further, in light of the above-described damage caused by PD, it is beneficial to more closely monitor PD events in order to repair or replace damaged components, which if left unattended may lead to arc flashes, explosion, or fire. However, in some locations, such as within switchgear cabinets, conventional PD sensors (acoustic or UV) are unable to get close to the likely location of the PD event, or easily measure the PD event, thus limiting traditional PD monitoring ability.
For example, in circuit breaker compartments, breaker arms make physical contact with a “contactor” having mechanical fingers that compress around a breaker arm, thus allowing current to flow across the connection. Such mechanical connection points are locations that are prone to PD due to the wear and tear and the loosening of parts through repeated use, or through imprecise manufacturing leading to current flow and voltage imbalances. PD events here can result in possible catastrophic arc flash failure. Significant challenges exist in detecting PD events in such locations, as the connection points are surrounded by a breaker arm enclosure that absorbs or attenuates the typical PD indicators (acoustic and UHF signals) that the PD antenna is detecting. As such, conventional PD solutions are less likely to detect low intensity PD events within a circuit breaker compartment. Further, conventional solutions are not able to detect the precise location (e.g. the breaker connection) where the PD event generated.
These limitations with the conventional detection approaches are, in part, due to regulations limiting the use of low voltage (LV) wiring into HV compartments for some classes of equipment, or in electrically noisy environments. Even in cases where regulations allow a PD antenna/sensor to be located within a HV compartment, a system that receives power through low voltage wiring cannot be placed directly on a HV bus bar or connection point without significant precautions and expense to reduce the risk of ground faults. Accordingly, PD antennas and sensors (and other sensor types) are traditionally located on a compartment wall, outside of the breaker arm enclosure, as described above. Further, the above-described sensor systems have historically not been able to measure all the parameters that lead to an arc flash in these environments. Therefore, the ability to develop failure patterns, and thus, to suggest preventative maintenance prior to a failure developing has been limited.